Sunday, February 28, 2016

I will be giving a talk on March 16th at 7:30 PM in Kane Hall on the UW campus on the history, science, and technology of weather forecasting as a fundraiser for KPLU. This will be a fun, educational exploration of the amazing story of of weather forecasting's evolution from folk wisdom to a quantitative science using supercomputers. General admission tickets are $25.00, with reserved seating and VIP tickets (including dinner) available at $100 and $ 1000, respectively. If you are interested in purchasing tickets, you can sign up here.
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There are many superlatives regarding Northwest weather: wettest region in the lower-48 states, world record annual snowfall (Baker), foggiest location in the U.S. (Cape Disappointment), and greatest non-tropical windstorm (Columbus Day 1962). But there is another one that few talk about: the longest spring in the nation.

Astronomical spring is, of course, the three month period from March 20/21 to June 20/21. But meteorological/biological spring can greatly differ from astronomical spring. Here in Seattle, spring arrives early and leaves late.

I like to tell folks that typically spring begins in western Washington the third week in February (let's say Feb. 25th) and ends in mid-July (local meteorologists like to use July 13th). Look outside now: flowers are blooming everywhere, weeds are growing, and the grass is getting longer. After Feb 25th, the chances of major flooding, low-level snow, and strong windstorms plummet. And we all know that June is often cloudy and cool and we don't make the real transition to reliable summer weather until mid-July. A spring of 4.5 months.

But let me go further. Not only are our springs the longest, but we probably have the longest springs in the nation. Prove it, you say? OK, let me try to do so.

First, we need an objective measure of spring. I will propose that spring is the period bracketed by two transitions:

the rise in maximum average daily temperatures from below 50F to above 70F

the rise in maximum average daily temperatures from below 70F to above 70F

Below 50F you feel cold without a good jacket or sweater, above 70F a tee shirt will do. Objective measures.

Locations where the daily high temperature never falls below 50F never have real winter and thus never truly have a spring. As illustrated by the map of maximum January daily temperatures (January is normally the coldest month), there is no real spring in much of California, southern Arizona and Nevada, Texas, and much of the SE U.S. Average high temperatures, typically rise about 50F each day. Region's without spring. Depressing.

Here in Seattle, the average high crosses 50F in late February and rises above 70F on June 23rd. About 4 months. A very gentle rise of temperature from New Years until summer.

In contrast, for Chicago the story is very different. The rise about 50F occurs on roughly March 17 and the climb above 70F around May 15th. Two months of spring, half of that enjoyed by Seattle.

New York? A rise above 50F on March 18th and a climb above 70F around May 20th. Two months.

Mile-high Denver? The transition across 50F on March 2 and the rise above 70F on May 15th. 2.5 months.

Portland, Oregon, which is warmer than Seattle? The rise above 50F on Feb 13th and the climb above 70F on June 1. 3.5 months

I have done this exercise for another two-dozen locations and the answer is the same:

NO MAJOR CITY IN THE U.S. HAS A LONGER SPRING THAN SEATTLE.

Imagine what the Seattle Chamber of Commerce could do with this information. Ads reveling in Seattle, the Springtime City, or Seattle City of Endless Spring, or Seattle's Eternal Spring. Almost enough to make you forget about the traffic.

The inquisitive among you might be asking: why does Seattle have such a long spring? I believe the answer goes like this:

Seattle's marine climate is dominated by the Pacific Ocean, whose surface temperature even in midwinter only drops to around 50F. We are isolated from the cold air of the continental interior and our air passed over the warm ocean rather the cool snow-covered interior. Our average wintertime maxima are relatively high (low to mid 40s) and so when the solar heating starts revving up in February, we quickly climb above the 50F mark. Thus, our early start to spring.

But the ocean cuts both ways, with the nearly constant 50F coastal waters working against any rapid increase in temperatures, even with the sun strengthening rapidly in March and April. More continental climates (and that is really most of the U.S.) don't have such an oceanic restraint and warm rapidly. Furthermore, the extensive low clouds of the eastern Pacific in spring and early summer (think June gloom) slow our warming further. Only in July, when the building East Pacific ridge causes less onshore flow (as northerly flow increases), does the clouds relent and we surge into summer territory.
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There are other related records that are worth noting, such as the longest spring roll (1428 feet) created in Indonesia. But in many ways, our spring record is far more impressive and important.

And there has been lots of coverage of places with endless summer, but spring, the season of life and rebirth, is certainly superior.

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Announcements

Northwest Weather WorkshopThe big local weather gathering is less than a month away (March 4-5, Seattle). If you are interested in attending, the agenda and registration information can be found here. This gathering is the place to be if you want to learn more about local weather research and operations. You MUST register to go.

Friday, February 26, 2016

As skiers can tell you, the region's snowpack is slowly fading under the onslaught of warmer than normal temperatures. Here is the latest snowpack status based on the SNOTEL observations. A range from 89 to 128% of normal for the water content of the snow. Unfortunately, with warmer temperatures and rain on the snow, coupled with inevitable settling, much of the snowpack has degraded into the familiar Cascade concrete, in contract to the wonderful powder earlier in the season.

But we are a lot better off than last year. Here are maps of the water content of our snowpack last year and this year on February 25th. Big difference, with more snow this year. And this year there has been WAY more total precipitation (including a lot of warm rain) that has filled our reservoirs.

Let's look at few at Stampede Pass (3850 ft) in the central WA Cascades and the far higher (5130 ft) Paradise Ranger Station near Mt. Rainier. A similar story at both for cumulative snowpack and precipitation. A huge surge in snowpack in December followed by a slow rise afterward. The observed amounts (blue lines) tracking near normal (red). Total precipitation (black line) well above normal (gray line). You notice that snowpack normally peaks in early April. This may not be true this year due to the expected warmer than normal El Nino conditions.

The next 72h will bring precipitation (today Friday and on Sunday), but conditions will be warm, so expect snow mainly at higher elevations (particularly about 5000 ft). Here are the predicted totals. The higher terrain in the British Columbia mountains do best.

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AnnouncementsNorthwest Weather WorkshopThe big local weather gathering is less than a month away (March 4-5, Seattle). If you are interested in attending, the agenda and registration information can be found here. This gathering is the place to be if you want to learn more about local weather research and operations. You MUST register to go.

Weather Forecasting: The History and TechnologyI will be giving a talk on March 16th at 7:30 PM in Kane Hall on the UW campus on the history, science, and technology of weather forecasting as a fundraiser for KPLU. General admission tickets will be $ 100 and VIP tickets that include dinner are $1000. If you are interested in purchasing tickets, you can sign up here.

Tuesday, February 23, 2016

There has been a flurry of media attention the last few days for a truly positive development: the National Weather Service now has two state-of-the-art supercomputers dedicated to weather prediction.

For years, I have complained in this blog about the National Weather Service gravely lagging in computer resources; three years ago, its weather computers had one-tenth the capacity of the European Center for Medium Range Forecasting (ECMWF). No longer. We are now modestly ahead of ECWMF.

One of the two new weather supercomputers

The two new supercomputers, called Luna and Surge, were purchased from a Seattle-based company, CRAY Inc. Large XC-40 models. Each runs at 2.9 petaflops (a quadrillion floating point operations per second). One machine handles the operational weather prediction models, the other is for backup and research. Each of these machines has nearly 100,000 processors. Impressive.

The implications of these new machines are substantial. With 3rd class supercomputers, the U.S. models were run at relatively coarse resolution. Our data assimilation systems (how one uses observations to create a physically realistic 3D description of the atmosphere) were 10-20 years behind ECMWF. The ensemble systems we used were too small, producing inferior probabilistic forecasts. Quite honestly, it was embarrassing that the nation with the largest weather research community and which had invented numerical weather prediction, allowed its weather computer resources to lapse in such a profound way.

But the embarrassment of inferior forecasts (such as Superstorm Sandy), encouraged Congress and NOAA management to finally deal with the situation and the new computers were one result. NOAA leaders such as Kathy Sullivan and Louis Uccellini have championed the new machines.

But to get maximum advantage from these new computers, their immense capacity needs to be used wisely. I have strong opinions on what wise use would mean, based on studying this issue for years and from my serving on a national advisory committee to the National Weather Service (UMAC). The computers could provide:

1. High resolution convection-allowing ensembles over the continental U.S., which could radically improve forecasting of thunderstorms.

But let me be honest: I have my concerns. There are some folks in the National Weather Service,who want to hold on to outdated legacy systems (such as their Short-Range Ensemble Forecasting (SREF) system and their poorly performing NMMB modeling system). There are plans to add an unproven NAM-RR system (Rapid Refresh system using the inferior NMM model) that will waste huge amount of resources. Others want to run the poorly performing Climate Forecast System (CFS) model out to 15 months (currently only 9 months). These computers should be seen as an opportunity to clean house and modernize and rationalize the National Weather Service modeling suite. An opportunity that should not be missed.

Quite frankly, even with these new machines, the National Weather Service is still short of computer power for providing the nation with state-of-the-science weather prediction. The European Center only does global prediction, while the National Weather Service does global, regional, and local prediction. Certainly, the NWS could profitably use 5-10 times more computer resource and the payback would be substantial.

The National Weather Service will soon decide on its new global model. There are two finalists: one (the NCAR MPAS model) would allow the NWS to combine forces with the vast U.S. research community to produce a superior modeling system. The other (NOAA GFDL FV3) would lead to isolation for decades, and the use of an inferior system at higher resolutions. I will blog about this critical decision soon.

But no matter what happens, these new computers will result in substantial weather forecasting improvements in the U.S., something that all Americans can note with some satisfaction.

Announcements

Weather Forecasting: Humanity's Greatest Achievement?I will be giving a talk on March 16th at 7:30 PM in Kane Hall on the UW campus on the history, science, and technology of weather forecasting as a fundraiser for KPLU. General admission tickets will be $ 100 and VIP tickets that include dinner are $1000. If you are interested in purchasing tickets, you can sign up here. Northwest Weather WorkshopThe big local weather workshop is less than a month away (March 4-5, Seattle). If you are interested in attending, the agenda and registration information can be found here. This gathering is the place to be if you want to learn more about local weather research and operations.

Sunday, February 21, 2016

According to the U.S. official Drought Monitor, large portions of eastern Oregon are still in severe drought (see below).

The U.S. Drought Monitor information is taken as gospel by the media and by local agencies and state governments. For example, the latest Oregon State Weekly Drought Report repeats the U.S. Drought Monitor information as if it is true.

The trouble is that virtually all factual, objective information (e.g., snowpack, precipitation, soil moisture, and reservoir levels) suggest just the opposite: the drought is over.

This really bothers me. Here we have an official U.S. government entity hyping drought and providing the public with information that is simply wrong. Let me prove this to you.

Let's start with the NOAA objective short-term and long-term drought indices: no drought in eastern Oregon, in fact it is wetter than normal in the short-term index.

The NWS Western Region Climate Center's graphic of % of normal precipitation shows that much of eastern Oregon and Washington had more than 150% of normal precipitation over the past 90 days. Only a few areas received less than 100%

The NOAA crop moisture index shows normal values east of the Cascade crest.

While the satellite-based GRACE soil moisture is ABOVE normal over most areas east of the Cascade crest

The bottom line of all this objective information is that there is absolutely no reason to suggest eastern Oregon is in severe or moderate drought. Or any kind of drought.

Why is the U.S. Drought Monitor different from the more rigorous objective measures described above? Because it is a SUBJECTIVE blend of many inputs, with a decided tendency to keep drought around even when reality says otherwise.

Why is the NOAA, USDA, and other Federal agencies supporting and distributing such inaccurate information? It is disturbing. Folks believe and are acting upon this incorrect information.

Announcements

Weather Forecasting: Humanity's Greatest Achievement?I will be giving a talk on March 16th at 7:30 PM in Kane Hall on the UW campus on the history, science, and technology of weather forecasting as a fundraiser for KPLU. General admission tickets will be $ 100 and VIP tickets that include dinner are $1000. If you are interested in purchasing tickets, you can sign up here. Northwest Weather WorkshopThe big local weather workshop is less than a month away (March 4-5, Seattle). If you are interested in attending, the agenda and registration information can be found here. This gathering is the place to be if you want to learn more about local weather research and operations.

Friday, February 19, 2016

There is a lot of talk about this being the wettest winter in Seattle history, including stories in the Seattle Times and on local TV stations. But, as in everything, there are subtleties, and such details may rob this year of the number one title.

The record winter talk was started by my colleagues at the National Weather Service, who noted in their twitter feed that during the last 24 hr Seattle had achieved a record rain total for December, January, and February (see details below for numbers as of this morning) for the period going back to 1894. At that point we were ahead by .01 inch, but we got a lot more rainfall today and there will be more during the rest of the month.

The biggest reason we broke the record was our extraordinarily wet December (11.21 inches, 5.86 inches above normal).

Now although some folks might think of December, January, and February as winter, it really doesn't represent meteorological winter in the Northwest or astronomical winter by the normal definition. November is a big rain month in our area, so lets look at the November through February total, which is much more meaningful (thanks again to Logan Johnson of the Seattle NWS office for these numbers). A somewhat different story, with this year falling back to fourth place (yes, still impressively wet!).

Today we had nearly a half-inch in addition and more rain will fall this month. There is a very good chance we will move into second or third place, but I suspect our chances of moving into first place are slight, with an extensive dry period ahead this week.

But using November 1 is still a bit artificial. Let's try using the start of the water year, October 1. That makes more sense, since we tend to be quite dry before that and many years see serious rain starting by mid-October. Again, the National Weather Service to the rescue....here are the totals since October 1st. Wow...we are in second place! Impressive. But we are quite a bit behind the leader (1951).

Now the competitive folks among you are asking, might we beat 1951 later in the season? It is possible, but we are starting 1.4 inches behind and next week will be pretty dry.

Any way you cut it, this has been a very wet winter...certainly in the top 5. But I would refrain from giving us the number one title, as some local media are trying to do. What makes it even more impressive is that this is a strong El Nino year, which generally results in modestly below normal precipitation after January 1.
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Public talk on March 16th in Seattle to raise funds for KPLU: Weather Forecasting: Humanity's Greatest Achievement?

I will be giving a talk on March 16th at 7:30 PM in Kane Hall on the UW campus on the history, science, and technology of weather forecasting. It
should be a fun presentation that will trace the development of weather
prediction from ancient times until now, including some offbeat aspects
you might not have heard about. The history of forecasting is quite
fascinating, including characters like Aristotle, Benjamin Franklin,
Captain Robert Fitzroy, and many others. Modern weather prediction is
perhaps humanity's greatest achievement, using the most powerful
supercomputers and billion-dollar satellites, dealing with phenomena
from the microscopic to the planetary scales. Weather forecasting is not
only science; there is a religious element to it as well and
represents a task that can only be accomplished when mankind works
together. The talk will end by describing how weather prediction
technology is being used to help understand and plan for climate change.

This talk is being given as a fundraiser to help raise the money needed to keep public radio station KPLU alive. General admission tickets will be $ 100 and VIP tickets that include dinner are $1000. If you are interested in purchasing tickets, you can sign up here.

Whether KPLU will survive depends upon the station raising 7 million dollars by June 30th. If they do, an independent KPLU will born and your favorite KPLU programming will be maintained and expanded. If KPLU fails to raise the funds, the station will be purchased by KUOW, which will fire the staff and take over the transmitters.

Wednesday, February 17, 2016

The Yakima River has experienced very high flows and brought some flooding the past few days, which is somewhat unusual for mid-February. Yakima flooding is normally a spring-time phenomenon, caused by melting as temperatures surge.

In this event, the Yakima first flooded closer the the Cascade foothills and then the water surge moved downstream. Right now, the Yakima gauges near Parker and Kona are near flood stage, breaking all time record flows for this period (see the area map, with red dots at these points, as well as the hydrographs (plots of flow with time)).

As you can imagine, the flux of water into the Yakima system was accompanied by a rapid rise of the Yakima reservoirs. Here is the proof.

So why the unusual event? Two big things. First, we had a temperature surge this week associated with warm, moist southwesterly flow. Yakima hit 67F on Monday, a record for the date, and 60F on Tuesday. With a healthy snowpack in the mountains, that resulted in a surge of melt.

In addition, there was substantial rain in the mountains, with the Cascades being hit by 200-400% of normal precipitation during the last week (see below).

For the Yakima and this event....the worst is nearly over. Temperatures will cool modestly the next few days and heaviest precipitation will be over northern CA, where it is acutely needed. We have enough.

Northwest Weather WorkshopThe big local weather workshop is less than a month away (March 4-5, Seattle). If you are interested in attending, the agenda and registration information can be found here. This gathering is the place to be if you want to learn more about local weather research and operations.

Monday, February 15, 2016

Yesterday, I took a very bumpy flight from Seattle to Dallas/Fort Worth--turbulence that was associated with a strong jet stream. Intriguingly, one look look at the satellite imagery should have told me that the seat belt sign would be on much of the flight. In this blog, I will talk about clear air turbulence, the impact of vertical wind shear, and something called transverse cloud banding. Throw phrases like that around at a party and your friends will either be impressed or walk away.

First, here is the path for my flight that started about 7 AM (1500 UTC Sunday Feb 14). The turbulence began once we reached initial cruising altitude (around 30,000 ft) over northern Oregon.

My aircraft was not the only one experiencing turbulence, as shown by the graphic below from the Aviation Weather Center-- there were lots of other reports (these are pireps...pilot reports of turbulence for 6 AM to 7:30 AM)

I knew that this was going to be in interesting flight with a strong jet stream along my route. Here are the wind at 30,000 feet at 7 AM, with the shading giving the wind speed and the barbs parallel to the winds (at least 125 knots in the core of strongest winds).

Where the winds increase rapidly with height one has large wind shear and often turbulence. One sign of that turbulence are transverse cloud bands....bands of clouds oriented roughly perpendicular to the wind direction. And we had a lot of such clouds along my flight path. Here are some examples in infrared, water vapor, and visible imagery at nearly the same time (around 8 AM)

The pilot tried several altitudes, as shown by this graphic of altitude and wind speed (from the web site: flight advisor). First, at 30,000 ft the flight was rough, then 36,000 ft (still rough), and later 39,000 ft...much better.

We were not in clouds during the turbulence....thus, it is called clear air turbulence. The radiosonde sounding at Boise, Idaho at 4 AM PST, show why things were better at 39,000 ft. If you can read the wind barbs, you can see a lot of wind shear (winds changing with height) below 10420 meters (34,000 ft). Energy for turbulence. At 11820 meters (38700 ft) there was much less vertical wind shear and we were entering the stable stratosphere. That is the fascinating thing about clear air turbulence...a little change in elevation can make a huge difference.

One good thing about the bumpy flight---riding the jet stream provided a lot of tail winds and we arrived a half-hour early.

Finally,a nother, more colorful, example of the banding structure is shown below.